A delta is formed primarily through the action of which natural feature?

A delta is primarily formed through the action of rivers as they deposit sediment at their mouths when they flow into a larger body of water, such as an ocean or a lake. As the river velocity decreases upon entering the standing water, the sediment carried by the river settles, accumulating over time to create landforms known as deltas.

This process is influenced by the river's flow rate, sediment supply, and the tidal or wave action of the receiving water body, which can affect sediment distribution. Other features like mountains may influence river pathways and sediment availability, but they do not create deltas themselves. Earthquakes and volcanoes may affect landforms and the environment, but they do not contribute to the formation of deltas in the same way that rivers do. Rivers are essential in the sediment transport and deposition that define a delta's characteristics.